Sealed switch



E. A. BALD SEALED swITc'H Nov. 26, 1957 Filed Ju1y'l8, i955 IN VEN TOR.

EDWARD A. BALD m2 0M 5 ATTOMEY United States Patent SEALED SWITCH Edward A. Bald, Freeport, Ill., assignor to Minneapolis- Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application July 18, 1955, Serial No. 522,657

3 Claims. (Cl. 200168) This invention relates to sealed switches and more particularly to means for providing movement through the seal for actuating the switch.

In many switch applications it is necessary to isolate the switching mechanism from its environment to assure reliable switch operation. The problem revolves largely around the structure to be employed to transmit movement to the switching mechanism. In the present invention a standard plunger actuated unitary switch is enclosed by a housing and a flexible seal closing an opening in the housing over the switch plunger has the additional function of forming a seal between the housing and the switch case. The space between the switch case and the housing is filled with a potting material, but the potting material is isolated from the space surrounding the plunger by the flexible seal. Hence, the switch is sealed to a degree closely approaching a true hermetic seal, while avoiding the necessity of employing the costly structure and manufacturing procedures necessary to attain a true hermetic seal. This invention represents an improvement over the disclosure of Martin application Serial No. 522,658, filed on even date herewith and assigned to the same assignee.

The object of the invention is to provide a sealed switch that is adapted for manufacture in small sizes, that is economical to manufacture and is of rugged construction.

Other objects will be evident from the specification and claims and from the drawing in which Figure 1 is a sectional elevation of a sealed switch incorporating the invention, and

Figure 2 is a fragmentary section taken on line 2-2 of Figure 1.

A unitary snap action switch including a plastic base 11 and a plastic cover 12 is disposed within a drawn sheet metal housing 15. The switch 10 is provided with mounting holes 16 and 17 which are aligned with corresponding holes in the housing 15. Switch 10 has an actuating plunger 19 surrounded by a boss 20 formed in the cover 12. Terminals 21 extend from the base 11 and suitable lead wires 22 are connected thereto. The switch 10 may be of the type disclosed in Patent 2,644,052 which, as manufactured, has a thickness of one quarter of an inch and a length of twenty-five thirty-seconds of an inch.

The housing is formed with a circular opening therein concentric with and overlying the plunger 19. The opening is closed by a sealing member 25 which comprises a cup shaped portion of silicone rubber including a generally flat diaphragm portion 26a and a generally cylindrical skirt portion 26b and a metal insert 27 which overlies plunger 19 and can be displaced to actuate the switch. The silicone rubber portion of member 25 is moulded to the housing 15 and to the insert 27 to form a seal preventing entry of foreign matter while providing the flexibility necessary for switch actuation. The rim of the skirt portion 26b engages the boss on the switch case as well as the upper surface of the switch cover surrounding the boss 20.

An epoxy resin 30 is used as potting material and fills 2,814,704 Patented Nov. 26, 1957 the space between the housing 15 and the switch 10 with the exception of the annular area around the plunger 19 dammed ofi by the sealing member 25. A suitable sealing material is applied to the juncture between the base 11 and cover 12 of switch 10 to prevent entry of the epoxy resin within the switch case prior to its solidification. The epoxy resin, in addition to completely sealing the switch case, also surrounds the sealing member 25 to prevent entry of foreign material between the switch cover 11 and sealing member 25.

I claim:

1. In a sealed switching device, a switch unit comprising a case and an actuating plunger extending through said case, a housing enclosing said switch unit, said housing having a circular opening therein in alignment with said plunger, means closing the opening in said housing including a first portion moulded to said housing in an annular area at the opening, a second portion overlying and adapted to engage said plunger, an annular third portion intermediate said first and second portions adapted to act as a diaphragm and deflect on movement of said second portion to actuate said plunger, a fourth cylindrical portion extending between said first portion and a surface portion of said switch case, said fourth portion being of compliant material adapted to sealingly engage an annular area of said case radially spaced from said plunger, and potting material within said housing and surrounding said switch with the exception of the portion thereof engaged by the fourth portion of said closing means.

2. In a sealed switching device, a switch unit comprising a case and an actuating member extending through said case, a housing enclosing said switch unit, said housing having an opening therein aligned with said actuating member, sealing means closing the opening including a first portion engaging said housing in an annular area around the opening, a second portion operatively engaging said actuating member and movable to actuate the switch, a third portion intermediate said first and second portions adapted to act as a diaphragm to permit movement of said actuating member, a fourth cylindrical portion extending axially between said first portion and a surface portion of said switch case, said fourth portion having a substantial free axial length and being of compliant material adapted to sealingly engage an annular area of said case radially spaced from said actuating member, and potting material within said housing and enveloping said switch case with the exception of the portion thereof dammed off by the fourth portion of said sealing means.

3. In a sealed switching device, a switch unit comprising a case and an actuating member extending through said case, a housing enclosing said switch unit, said housing having an opening therein aligned with said actuating member, sealing means closing the opening including a first portion moulded to said housing in an annular area around the opening, a second portion operatively engaging said actuating member and movable to actuate the switch, a third portion intermediate said first and second portions adapted to act as a diaphragm to permit movement of said actuating member, a fourth cylindrical portion extending axially between said first portion and a surface portion of said switch case, said fourth portion having a substantial free axial length and being of compliant material adapted to sealingly engage an annular area of said case radially spaced from said actuating member, and potting material within said housing and enveloping said switch case with the exception of the portion thereof dammed off by the fourth portion of said sealing means.

References Cited in the file of this patent UNITED STATES PATENTS 2,740,872 Brodsky et a1 Apr. 3, 1956 2,773,955 Haydon et a1. Dec. 11, 1956 

